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/*
* file: polygon.c
* description: polygon module
* author: A. T. Campbell, III
* date: February 9, 1995
*/
#include <math.h>
#include <stdlib.h>
#include "polygon.h"
#include "brep.h"
#include "bspvector.h"
/* copy a polygon */
void
PolygonCopy3f(Polygon3f *src, Polygon3f *dest)
{
int i;
dest->numverts = src->numverts;
for (i = 0; i < src->numverts; i++)
Vcopy3f(src->verts[i], dest->verts[i]);
Vcopy3f(src->plane_normal, dest->plane_normal);
dest->material_index = src->material_index;
dest->facesForward= src->facesForward;
}
/* allocate memory */
Polygon3f *
PolygonCreate3f(void)
{
Polygon3f *p;
p = (Polygon3f *)malloc(sizeof(Polygon3f));
if (p != NULL) {
p->numverts = 0;
Vset3f(0., 0., 0., p->plane_normal);
p->material_index = 0;
}
return p;
}
/* split a convex polygon by a plane */
void
PolygonCutConvex3f(Polygon3f *p, Vec3f pntOnPlane, Vec3f planeNormal,
int maxPieces,
int *numpos, Polygon3f *posarr[],
int *numneg, Polygon3f *negarr[])
{
E_side side;
Vec4f coeffs;
side = PolygonSidePlane3f(p, pntOnPlane, planeNormal);
if (side == sidePositive) {
*numpos = 1;
*numneg = 0;
posarr[0] = PolygonCreate3f();
PolygonCopy3f(p, posarr[0]);
}
else if (side == sideNegative) {
*numpos = 0;
*numneg = 1;
negarr[0] = PolygonCreate3f();
PolygonCopy3f(p, negarr[0]);
}
else if (side == sideBoth) {
/* Dave Carver gets to write this one */
*numpos = *numneg = 0;
posarr[0] = PolygonCreate3f();
negarr[0] = PolygonCreate3f();
Vset4f (planeNormal[0], planeNormal[1], planeNormal[2],
-Vdot3f(pntOnPlane,planeNormal),coeffs);
brep_split(planeNormal, p->numverts, p->verts, UNIVEPS,
&(posarr[0]->numverts), posarr[0]->verts,
&(negarr[0]->numverts), negarr[0]->verts);
if (posarr[0]->numverts == 0)
PolygonDestroy3f(posarr[0]);
else {
*numpos = 1;
Vcopy3f(p->plane_normal, posarr[0]->plane_normal);
posarr[0]->material_index = p->material_index;
}
if (negarr[0]->numverts == 0)
PolygonDestroy3f(negarr[0]);
else {
*numneg = 1;
Vcopy3f(p->plane_normal, negarr[0]->plane_normal);
negarr[0]->material_index = p->material_index;
}
}
else { /* side = sideNeither */
*numpos = *numneg = 0;
}
}
/* free memory */
void
PolygonDestroy3f(Polygon3f *p)
{
if (p != NULL)
free((char *)p);
}
/* compute normal to a polygon */
/* use Newell's formulation (Foley, Van Dam, Feiner, & Hughes, pp. 477) */
void
PolygonNormal3f(Polygon3f *p, Vec3f normv)
{
Vec3f *v;
int i, ip1, n;
if (p == NULL) return;
n = p->numverts;
v = p->verts;
Vset3f(0., 0., 0., normv);
i = n - 1;
for (ip1 = 0; ip1 < n; ip1++) {
normv[0] += (v[i][1] - v[ip1][1]) *
(v[i][2] + v[ip1][2]);
normv[1] += (v[i][2] - v[ip1][2]) *
(v[i][0] + v[ip1][0]);
normv[2] += (v[i][0] - v[ip1][0]) *
(v[i][1] + v[ip1][1]);
i = ip1;
}
Vnormalize3f(normv);
}
/* print information about a polygon */
void
PolygonPrint3f(FILE *fp, Polygon3f *p)
{
int i;
fprintf(fp, "numverts=%d material_index=%d\n", p->numverts, p->material_index);
for (i = 0; i < p->numverts; i++)
fprintf(fp, "%f %f %f\n",
p->verts[i][0], p->verts[i][1], p->verts[i][2]);
}
/* set the vertices of a polygon */
void
PolygonSet3f(Polygon3f *p, int n, Vec3f v[])
{
int i;
p->numverts = n;
for (i = 0; i < n; i++)
Vcopy3f(v[i], p->verts[i]);
}
/* determine what side of a plane a polygon is on */
E_side
PolygonSidePlane3f(Polygon3f *p, Vec3f pntOnPlane, Vec3f planeNormal)
{
int positive, negative;
Vec4f planeCoeffs;
float testVal;
int i;
/* compute planar equation */
Vset4f(planeNormal[0], planeNormal[1], planeNormal[2],
-Vdot3f(pntOnPlane, planeNormal), planeCoeffs);
/* test all vertices */
positive = negative = 0;
for (i = 0; i < p->numverts; i++) {
testVal = planeCoeffs[0]*p->verts[i][0] +
planeCoeffs[1]*p->verts[i][1] +
planeCoeffs[2]*p->verts[i][2] +
planeCoeffs[3];
if (testVal < 0)
negative = 1;
if (testVal > 0)
positive = 1;
}
/* determine return value */
if (positive && !negative)
return sidePositive;
else if (negative && !positive)
return sideNegative;
else if (negative && positive)
return sideBoth;
else
return sideNeither;
}
/* translate the vertices of a polygon */
void
PolygonTranslate3f(Polygon3f *p, Vec3f delta)
{
int i;
for (i = 0; i < p->numverts; i++)
Vadd3f(delta, p->verts[i], p->verts[i]);
}
/* get the bounding box of a polygon */
void PolygonBBox3f(Polygon3f *p, Vec3f low, Vec3f high) {
int i;
if (p->numverts <1) return;
Vcopy3f(p->verts[0],low);
Vcopy3f(p->verts[0],high);
for (i=1; i <p->numverts; i++) {
Vmin3f(low,p->verts[i],low);
Vmax3f(high,p->verts[i],high);
}
}
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